JPH02169834A - Inner-cylinder direct jet type spark ignition engine - Google Patents

Abstract

PURPOSE:To perform satisfactory combustion by jetting the total required fuel jet amount when it is not more than a first jet amount, that is, under a low load, and jetting the fuel jet amount while being distributed to intake and compression processes when it is less than a second and not less than a third jet amount, that is, under a medium load. CONSTITUTION:In a control unit 20, a fuel pressure detected by a sensor 27, an engine speed obtained from a crank angle signal of a sensor 29, accelerator opening angle detected by a sensor 30, etc., are input to compute a fuel jet amount. When the required fuel jet amount is not more than a first jet amount which is a sum of a minimum compression process jet amount for an ignition plug 65 enough to form ignitable air fuel mixture and a minimum intake process jet amount enough to propagate frame, a fuel jet valve 5 is controlled such that the total amount is jet during compression process. When the required jet amount is not less than a third jet amount which is less than a second jet amount enough to form an even air-fuel mixture and not less than the first amount, the total amount is jet while being distributed to the intake and compression processes. Satisfactory ignition and combustion are thus performed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an in-cylinder direct injection spark ignition engine.

[Conventional technology]

JP-A-60-30420 discloses an in-cylinder direct injection spark ignition engine in which the fuel injection timing is advanced as the load increases. In this engine, during low load operation, fuel is injected near the spark plug in the latter half of the compression stroke to form a combustible air-fuel mixture near the spark plug to ensure good ignition and combustion. During operation, fuel is injected during the first half of the intake stroke, allowing the fuel to diffuse sufficiently into the cylinder to increase air utilization and improve output.

[Problem to be solved by the invention]

In this engine, during medium load operation, fuel is injected from the latter half of the intake stroke to near the beginning of the compression stroke, and this injected fuel diffuses into the cylinder metal body. However, since the fuel injection amount during medium load operation is not as large as that during high load operation,
There is a problem in that the mixture formed by the fuel diffused throughout the cylinder becomes too lean, making ignition and combustion difficult.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides an in-cylinder direct injection spark ignition engine that can split-inject the required fuel injection amount depending on the engine operating state into the intake stroke and the compression stroke.
The required fuel injection amount is the minimum compression stroke fuel injection amount that can form a mixture that can be ignited by the ignition plug, and the minimum intake stroke fuel injection amount that allows the ignition flame to propagate when uniformly diffused in the cylinder. If the required fuel injection amount is less than or equal to the first injection amount, which is the sum of If the required injection amount is smaller than the second injection amount, which is the minimum fuel injection amount, and is greater than or equal to the first injection amount, the required injection amount is divided into the intake stroke and the compression stroke, and the injection is performed. That's what I do.

[Operation] When the required fuel injection amount is less than or equal to the first injection amount, the entire required fuel injection amount is injected in the compression stroke, forming a stratified air-fuel mixture that can be ignited and combusted.

When the required fuel injection amount is smaller than the second injection amount and greater than or equal to the third injection amount, the required fuel injection amount is divided into an intake stroke and a compression stroke and injected. The fuel injected during the intake stroke forms a lean mixture for flame propagation throughout the cylinder, and the fuel injected during the compression stroke forms a relatively rich mixture for ignition near the spark plug.

〔Example〕

FIG. 1 shows a configuration diagram of a four-cylinder gasoline engine employing an embodiment of the present invention. In the figure, 1 is the engine body, 2 is the surge tank, 3 is the air cleaner, and 4 is the surge tank 2.
5 is an electrostrictive fuel injection valve that injects fuel into each cylinder; 65 is a spark plug; 6 is a high-pressure reservoir tank; A high-pressure fuel pump whose discharge pressure can be controlled for pressure-feeding to the reservoir tank 6; 9 is a fuel tank; 10 is a conduit 11;
A low-pressure fuel pump is shown which supplies fuel from the fuel tank 9 to the high-pressure fuel pump 7 via the fuel tank 9, respectively. Low pressure fuel pump 10
The discharge side of each fuel injection valve 5 is connected to a piezoelectric element cooling introduction pipe 12 for cooling the piezoelectric element of each fuel injection valve 5 . The piezoelectric element cooling return pipe 13 is connected to the fuel tank 9 , and the fuel flowing through the piezoelectric element cooling introduction pipe 12 is recovered into the fuel tank 9 via the return pipe 13 . Each branch pipe 14 connects each high pressure fuel injection valve 5 to a high pressure reservoir tank 6.

The electronic control unit 20 consists of a digital computer and has 8 ports connected to each other by a bidirectional bus 21.
(Read-on memory) 22, RAM (Random access memory> 23, CPU (microprocessor) 24,
A human power port 25 and an output port 26 are provided. A pressure sensor 27 attached to the high-pressure reservoir tank 6 detects the pressure within the high-pressure reservoir tank 6, and its detection signal is input to the input port 25 via the A/D converter 28. The output pulse of the crank angle sensor 29, which generates an output pulse proportional to the engine speed Ne, is output from the human power port 2.
5 is input. Opening degree θ of the accelerator pedal (not shown)
Accelerator opening sensor 30 that generates an output voltage according to A
The output voltage is input to the input port 25 via the A/D converter 31. On the other hand, each fuel injection valve 5 is connected to the output port 26 via each drive circuit 34. Further, each spark plug 65 is connected to the output port 26 via each drive circuit 35.

Further, the high-pressure fuel pump 7 is connected to the output port 26 via a drive circuit 36.

FIG. 2 shows a side sectional view of the fuel injection valve 5. Referring to FIG. 2, 40 is a needle inserted into a nozzle 50;
41 is a pressure rod, 42 is a movable plunger, 43 is a compression spring disposed in the spring housing chamber 44 and presses the needle 40 downward, 45 is a pressure piston, 46 is a piezoelectric element, and 47 is a movable plunger. a pressurized chamber 48 formed between the top of 42 and the piston 45 and filled with fuel;
indicate needle pressurization chambers, respectively. The needle pressurizing chamber 48 is connected to the high-pressure reservoir tank 6 (FIG. 1) via the fuel passage 49 and the branch pipe 14, so that the high-pressure fuel in the high-pressure reservoir tank 6 flows through the branch pipe 14 and the fuel passage 49. and is supplied into the needle pressurizing chamber 48. When the piezoelectric element 46 is charged, the piezoelectric element 46 expands, thereby increasing the fuel pressure within the pressurizing chamber 47.

As a result, the movable plunger 42 is pressed downward, and the nozzle port 53 is held closed by the needle 40. On the other hand, when the electric charge charged in the piezoelectric element 46 is discharged, the piezoelectric element 46 contracts,
The fuel pressure within the pressurizing chamber 47 decreases. As a result, the movable plunger 42 rises, the needle 40 rises, and fuel is injected from the nozzle port 53.

FIG. 3 shows a longitudinal sectional view of the engine of the first embodiment.

Referring to FIG. 3, 60 is a cylinder block, 61 is a cylinder head, 62 is a piston, and 63 is a piston 62.
0 a substantially cylindrical recess formed on the top surface; 64 is a piston 62;
The cylinder chambers formed between the top surface and the inner wall surface of the cylinder Rad 61 are shown. The ignition plug 65 is attached to a substantially central portion of the cylinder head 61 facing the cylinder chamber 64. Although not shown in the drawing, an intake boat and an exhaust boat are formed inside the cylinder head 61, and intake valves 66 (see FIG. 5(a)) are provided at the openings of these intake boats and exhaust boats into the cylinder chamber 64, respectively. ) and an exhaust valve are arranged. The fuel injection valve 5 is a swirl type fuel injection valve, and injects fuel in the form of a spray with a large spread angle and a weak penetration force.

The fuel injection valve 5 is oriented obliquely downward to the cylinder chamber 64.
The spark plug 65 is disposed at the top of the spark plug 65, and is disposed so as to inject fuel toward the vicinity of the spark plug 65. Further, the fuel injection direction and fuel injection timing of the fuel injection valve 5 are determined so that the injected fuel is directed toward the recess 63 formed at the top of the piston 62.

FIG. 4 shows control patterns for compression stroke injection and intake stroke injection in this embodiment. Referring to Figure 4, the horizontal axis represents the engine load, and in Figure 4, the load is the fuel injection amount Q.
and the fuel injection amount Q is plotted on the vertical axis. From low load to the third injection amount Q, fuel is injected only in the compression stroke. Compression stroke fuel injection amount Q
c is gradually increased up to Qs. In the fuel injection amount Qs, the compression stroke fuel injection amount Qc is Q. At the same time, the intake stroke fuel injection amount Q1 is suddenly increased to Q. Q is the fuel injection amount near medium load, and is expressed by the following equation as the sum of Q and Ol.

QS = Qo + Qp Here, Qo is the minimum amount of fuel injection during the compression stroke that can form a mixture that can be ignited by the spark plug 65, and Q is the minimum fuel injection amount during the compression stroke that can form a mixture that can be ignited by the spark plug 65. This is the minimum intake stroke fuel injection amount that allows the ignition flame by the ignition plug 65 to propagate when it spreads. Therefore, Qs is also the first injection amount, and in this embodiment, the first injection M and the third injection amount match.

In a load region where the fuel injection amount is larger than Qs, the required fuel injection iQ is divided into the compression stroke and the intake stroke and injected, and the compression stroke fuel injection lQ is performed. is constant regardless of the load, and the intake stroke fuel injection amount Q is increased as the load increases.

In a load region lower than Q5 near the medium load, as shown in FIG. 3, compression stroke injection is performed in the latter half of the compression stroke, and fuel is directed from the fuel injection valve 5 toward the ignition plug 65 and the concave portion 63 on the top surface of the piston 62. fuel is injected. This injected fuel has a weak penetrating force, and since the pressure inside the cylinder chamber 64 is high and the air flow is weak, the injected fuel is unevenly distributed in the region K near the ignition plug 65. The fuel distribution within this region is non-uniform, varying from a rich mixture layer to an air layer.
Within this region, there is a combustible air-fuel mixture layer near the stoichiometric air-fuel ratio that is most combustible. Therefore, the combustible mixture layer near the ignition plug 65 is easily ignited, and the ignition flame propagates throughout the heterogeneous mixture layer to complete combustion. In this way, in a low load region lower than medium load, fuel is injected near the spark plug 65 in the latter half of the compression stroke, thereby forming a combustible mixture layer near the spark plug 65, thus achieving good ignition and This results in combustion.

On the other hand, near the medium load Q, in the higher load region, the fifth
As shown in the figure, intake stroke injection is performed at the beginning of the intake stroke (FIG. 5(a)), and the fuel injection valve 5 causes the spark plug 65 to
Then, fuel is injected toward the recess 63 on the top surface of the piston 62. This injected fuel is a spray-like fuel with a large spread angle and a weak penetration force, and a part of the injected fuel floats in the cylinder chamber 64 and the other part collides with the recess 63. These injected fuels are diffused into the cylinder chamber 64 by the turbulence R in the cylinder chamber 64 caused by the intake air flow flowing into the cylinder chamber 64 from the intake boat, and are dispersed into the premixture P during the period from the intake stroke to the compression stroke. is formed (Fig. 5(b)
). The air-fuel ratio of this premixture P is such that an ignition flame can propagate.

In addition, in the state shown in Fig. 5(b), the central axis of the injected fuel is directed toward the cylinder wall, so if the penetration force of the injected fuel is strong, there is a risk that part of the spray may directly adhere to the cylinder wall. There is. In this embodiment, there is no particular problem because the injection is performed with a relatively weak penetration force, but in the embodiment of the present invention, this period is set as a non-injection period to enhance the effect of preventing fuel from adhering to the cylinder wall surface. There is. Subsequently, compression stroke injection is performed in the latter half of the compression stroke (FIG. 5(C)), and fuel is injected from the fuel injection valve 5 toward the vicinity of the spark plug 65 and the recess 63 on the top surface of the piston 62. This injected fuel is originally directed toward the ignition plug 65 and has a weak penetrating force, and the pressure inside the cylinder chamber 64 is high, so the injected fuel is unevenly distributed in the area K near the ignition plug 65. The fuel distribution within this region is also non-uniform and changes from a rich mixture layer to an air layer, so within this region there is a combustible mixture layer near the stoichiometric air-fuel ratio where combustion is most likely to occur. Therefore, when the combustible mixture layer near the ignition plug 65 is ignited, combustion proceeds centering around the heterogeneous mixture region K (FIG. 5(d)). In this combustion process, the premixture P
The flame spreads and combustion is completed. In this manner, in medium load and high load regions, fuel is injected at the beginning of the intake stroke to form a mixture for flame propagation throughout the cylinder chamber 64, and fuel is injected at the latter half of the compression stroke. A relatively rich air-fuel mixture is formed near the ignition plug 65 to form an air-fuel mixture for ignition and flame kernel formation. In this way, good ignition and combustion with high air utilization efficiency can be obtained. Particularly during medium load operation, if the entire required injection amount is injected during the intake stroke or the first half of the compression stroke as in conventional engines, the injected fuel will diffuse throughout the cylinder chamber 64; The problem is that the air-fuel mixture that is formed becomes too lean, making ignition and combustion difficult. On the other hand, if the entire required injection amount is injected in the latter half of the compression stroke during medium-load operation, there are problems such as a large amount of smoke being generated, and the air utilization rate not being able to be increased, making it impossible to obtain a sufficiently high output. be. In this embodiment, as mentioned above, during medium load operation, by splitting injection into the intake stroke and compression stroke, high output can be obtained due to good ignition and combustion with high air utilization rate.

In addition, near medium loads, the homogeneous air-fuel mixture formed by the fuel injected during the intake stroke may have an air-fuel ratio that is thinner than the air-fuel ratio that allows ignition and is sufficient to allow flame propagation, improving fuel efficiency through lean combustion. Can be done.

Further, since split injection is performed using a fuel injection valve that supplies fuel near the ignition plug, this embodiment can be executed with one fuel injection valve for one cylinder.

In addition, when performing intake stroke injection when the fuel injection amount is less than Qs, the intake air is throttled to reduce the amount of intake air in order to form a mixture that can ignite and spread flame. It is necessary to maintain the air-fuel ratio. However, when the intake air is throttled to maintain the air-fuel ratio, pumping loss occurs. In this embodiment, only compression stroke injection is performed when the fuel injection amount is equal to or less than Qs, so that such pumping loss can be reduced.

Note that in a direct injection internal combustion engine, combustion is possible even in an excess air condition due to stratified combustion, so in this example, the case where the intake air amount is not throttled is explained. In order to reduce engine heat loss at low temperatures, and further for EGR, intake air may be throttled in some operating regions. However, since the intake throttle in this case is smaller than the intake throttle for maintaining the air-fuel ratio described above, the pumping loss does not increase much.

FIG. 6 shows a routine for executing this embodiment. The routine shown in FIG. 6 is executed by interrupts at every fixed crank angle. Referring to FIG. 6, first, in step 70, the engine speed NE and the accelerator opening θA are determined.
is loaded. In step 71, the required fuel injection amount Q is calculated from the map I (FIG. 7) based on NE and θA. Referring to FIG. 7, a increases as θA increases, and has a maximum value when NE is around 4000 rpm.

In step 73, it is determined whether the required fuel injection amount Ω is equal to or less than Qs (see FIG. 4). If the determination is affirmative, the entire required fuel injection amount Q is injected in the compression stroke from step 74 onwards. In step 74, the compression stroke fuel injection amount Q
The requested fuel injection i1Q is stored in c. In step 75, the intake stroke fuel injection amount Q1 is set to zero. In step 76, the compression stroke fuel injection period Tc changes from map 2 (FIG. 8) to Q.

Calculated based on. Referring to FIG.

Q. increases linearly as . In step 77, the intake stroke fuel injection period T+ is set to zero. In step 78, the compression stroke fuel injection amount Q is determined from map 3 (FIG. 9). The compression stroke fuel injection start timing TSc is calculated based on the engine speed NE and the present routine ends. Referring to FIG. 9, TSc is shown as an injection advance angle from compression top dead center. TSo is NE and Q. speeds up as the value increases.

If a negative determination is made in step 73, the required fuel injection IQ is divided into the intake stroke and the compression stroke and injected in steps 79 and thereafter. Step 79 is the compression stroke fuel injection amount Q. Q, (see Figure 4) is inserted into. In step 80, Q-Q is entered into the intake stroke fuel injection amount Q1. That is, the intake stroke fuel injection amount Q+ and the compression stroke fuel injection amount Q. The sum of the required injection amount Q is made to be the required injection amount Q. In step 81, Q from map 2 (Figure 8). The compression stroke fuel injection period Tc is calculated based on. In step 82, the intake stroke fuel injection period TI is calculated based on map 2 (FIG. 8) to Q. Referring to FIG. 8, TI increases linearly as Q increases. In step 83, the compression stroke fuel injection start timing TS is determined from the map 4 (FIG. 10) based on the requested injection iQ and the engine speed NE.

is calculated. Referring to FIG. 10, TS is shown as the injection advance from compression top dead center, and TSc is advanced as NE and Q increase.

In step 84, the intake stroke fuel injection start timing TS is calculated from the map 5 (FIG. 11) based on the intake stroke fuel injection amount Q1 and the engine speed NE. Referring to FIG. 11, TS is shown as the injection advance from compression top dead center, and TSI is advanced as NE increases. In map 5, TSI is not changed by Q+. This is because in intake stroke injection, there is sufficient time for the fuel to diffuse and form an air-fuel mixture, so there is no need to change it depending on the Q factor.

The above step routine is completed, and fuel injection is executed by another routine (not shown).

FIG. 12 shows a routine for calculating ignition timing. The routine shown in FIG. 12 is executed by an interrupt at every fixed crank angle. Referring to FIG. 12, in step 90, the engine speed NE and requested fuel injection iQ are read. In step 91, map 6 (
The ignition timing is calculated from Fig. 13). Referring to FIG. 13, the horizontal axis shows the required fuel injection amount Q, and the vertical axis shows the ignition advance from compression top dead center. As for the ignition timing, the advance angle is increased as Q decreases, and the advance angle is increased as NE increases.

Next, a second embodiment will be described. The second example is
This embodiment differs from the first embodiment in the recesses formed at the tops of the fuel injection valve 5 and the piston 62, and the differences will be explained. The concave combustion chamber 67 formed at the top of the piston has a double structure of a large-diameter shallow dish part 68 on the upper side and a deep dish part 69 on the lower side formed in the center of the shallow dish part 68, Deep dish part 6
9 is formed to have a smaller diameter than the shallow dish portion 68.

The intake port (not shown) is a swirl port,
The fuel injection valve 5 has a multi-hole nozzle. Therefore, the fuel injection valve 5 injects a relatively rod-shaped fuel having a relatively strong penetration force and a small spread angle. The fuel injection valve 5 is arranged at the top of the cylinder chamber 64 so as to face diagonally downward.

Further, the fuel injection direction and fuel injection timing of the fuel injection valve 5 are determined so that the injected fuel is directed into the combustion chamber 67. The ignition plug 65 is connected to the concave combustion chamber 6 at the top dead center of the piston 62
7.

The control pattern for compression stroke injection and intake stroke injection in the second embodiment is similar to that in the first embodiment (see FIG. 4).

Referring to FIGS. 4 and 14, in the middle load vicinity Q and lower load region, the entire required injection amount is injected from the fuel injection valve 5 toward the combustion chamber 67 in the latter half of the compression stroke. The fuel injection timing is delayed so that most of the fuel is injected into the deep dish portion 69. The fuel adhering to the inner wall surface of the deep dish portion 69 evaporates and becomes atomized, forming a rich and light mixture layer including a flammable region in the combustion chamber 67. A part of this mixture layer is ignited by the ignition plug 65, and the main Good combustion is completed within the deep dish portion 69.

Near medium load Q, in a higher load region, as shown in FIG. 15, intake stroke injection is performed at the beginning of the intake stroke (FIG. 15(a)), and the fuel injector 5 is injected into the combustion chamber 67.
Fuel is injected towards the The injected fuel F mainly collides with the shallow dish portion 68, and a portion of it is reflected into the cylinder chamber 64.
The other part adheres to the wall surface of the shallow dish portion 68 and is evaporated and atomized by heating from the wall surface. These fuels form a premixture P during the period from the intake stroke to the compression stroke due to the intake swirl SW and the turbulence R of the intake flow (FIG. 15(b)). The air-fuel ratio of this premixture P is set to such an extent that the ignition flame can propagate, as in the first embodiment. When the suction vortex SW is strong, a premixture is formed that is rich near the outer periphery of the cylinder chamber 64 and thin near the center.

Note that if the intake stroke injection timing is advanced and the fuel is injected when the piston 62 is closer to the top dead center, most of the fuel will be injected into the deep dish portion 69; The mixture is pre-vaporized in the section 69.

Subsequently, compression stroke injection is performed in the latter half of the compression stroke (FIG. 15(C)), and most of the fuel is injected into the deep dish portion 69. The fuel adhering to the inner wall surface of the deep dish portion 69 is vaporized by heating from the wall surface and compressed air, and is diffused and mixed by the vortex SW, forming a heterogeneous mixture layer with a rich and light concentration including a flammable region. A part of this mixture layer is ignited by the spark plug 65,
Combustion of the heterogeneous mixture layer progresses (FIG. 15(d)).

As the flame B formed by this combustion develops inside the deep dish part 69, it propagates into the surrounding premixture, and further, due to the reverse squish flow S, the combustion progresses to the outside of the deep dish part 69.

In addition, when the compression stroke injection timing is advanced and the fuel is injected into both the shallow dish part 68 and the deep dish part 69, the flame is widely distributed in the shallow dish part 68 and the deep dish part 69, and the premixture is affected. Flame propagation can be made easier.

The control pattern for the compression stroke injection and the intake stroke injection is the control pattern shown in FIG. 4 in both the first and second embodiments, but is not limited to this, and may be, for example, the patterns shown in FIGS. 16 to 19. is possible. Similar to FIG. 4, the horizontal and vertical axes in these figures indicate the load and the fuel injection amount, respectively.

The control pattern shown in FIG. 16 is similar to the control pattern shown in FIG. 4 up to the second injection amount Q)I. When the load is extremely high (QH or above), the amount of fuel injected is large and the concentration of the premixture in the cylinder chamber formed by intake stroke injection is high enough for ignition, so compression stroke injection for ignition is stopped. , the entire required fuel injection amount is injected during the intake stroke. Q is the minimum intake stroke fuel injection amount that can form a homogeneous mixture that can be ignited by the spark plug even when the fuel is uniformly diffused in the cylinder chamber.

The control pattern shown in FIG. 17 is the control pattern shown in FIG. 16 in which the compression stroke fuel injection amount is gradually decreased from load Q to Qo. As the intake stroke fuel injection amount increases as the load increases, the premixture becomes richer.

Therefore, the compression stroke fuel injection amount required for stable ignition can be gradually reduced.

The control patterns in Figs. 18 and 19 are as shown in Figs. 4 and 1.
Unlike the control patterns of FIGS. 6 and 17, the third injection amount is larger than the first injection amount.

In the control pattern shown in Fig. 18, the entire required injection fuel amount is injected only by compression stroke injection until the third injection amount Qx, which is larger than the first injection amount Qs, and when QX is exceeded, the compression stroke fuel injection amount becomes Qx. Fuel that is kept constant and exceeds Qx is injected on the intake stroke. The compression stroke maximum fuel injection amount Qx is sufficiently large, and the combustion of the air-fuel mixture formed by this compression stroke injection causes a sufficient flame to grow. It is possible to propagate

The control pattern shown in FIG. 19 is the same as the control pattern shown in FIG. 18, in which the compression stroke fuel injection amount is reduced upward from the load Q, so that only intake stroke injection occurs at the maximum load.

As the load increases, the intake stroke fuel injection amount increases, which enriches the premixture and facilitates flame propagation, making it possible to gradually reduce the compression stroke fuel injection amount required for stable ignition.

〔Effect of the invention〕

As described above, according to the present invention, good ignition and combustion can be obtained when the fuel injection amount is equal to or less than the first injection amount, for example, at a low load.

On the other hand, when the fuel injection amount is smaller than the second injection amount and greater than or equal to the third injection amount, good ignition is achieved by the air-fuel mixture formed by the fuel injected during the compression stroke, especially at medium load, and the intake air is Combustion with high air utilization can be achieved by the mixture formed by the fuel injected during the stroke.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the engine of the present invention, Fig. 2 is a longitudinal sectional view of a fuel injection valve, Fig. 3 is a longitudinal sectional view of the engine of the first embodiment, and Fig. 4 is a longitudinal sectional view of the engine of the first embodiment. A diagram showing an example of a control pattern for compression stroke injection and intake stroke injection, FIG. 5 is an explanatory diagram of the operation of the first embodiment, FIG. 6 is a flowchart for controlling fuel injection, and FIG. 7 is a flowchart for controlling fuel injection. Figure 8 is a diagram showing the relationship between intake stroke and compression stroke fuel injection amount and intake stroke and compression stroke fuel injection time. Figure 9 is a diagram showing the relationship between intake stroke and compression stroke fuel injection time. A diagram showing the relationship between the injection amount and the compression stroke fuel injection start timing, FIG. 10 is a diagram showing the relationship between the required fuel injection amount and the compression stroke fuel injection start timing, and FIG. 11 is a diagram showing the relationship between the intake stroke fuel injection amount and the compression stroke fuel injection start timing. A diagram showing the relationship between the intake stroke fuel injection start timing, FIG. 12 is a flowchart for calculating the ignition timing, FIG. 13 is a diagram showing the relationship between the required fuel injection amount and the ignition advance angle, and FIG. 14 is the second
FIG. 15 is an explanatory diagram of the operation of the second embodiment, and FIGS. 16 to 19 are diagrams showing other examples of control patterns for compression stroke injection and intake stroke injection. It is.

Claims (1)

[Claims] In an in-cylinder direct injection spark ignition engine that can split-inject a required fuel injection amount depending on the engine operating state into an intake stroke and a compression stroke, the required fuel injection amount forms an air-fuel mixture that can be ignited by a spark plug. the minimum possible compression stroke fuel injection amount;
If the injection amount is less than the first injection amount, which is the sum of the minimum intake stroke fuel injection amount that allows the ignition flame to propagate when homogeneously diffused in the cylinder, the entire required fuel injection amount is injected in the compression stroke. , the required fuel injection amount is smaller than a second injection amount that is the minimum fuel injection amount that can form a homogeneous mixture that can be ignited by the spark plug in the entire cylinder, and is greater than or equal to the first injection amount If the required injection amount is equal to or greater than a third injection amount, the required injection amount is divided into an intake stroke and a compression stroke and the injection is performed.